Tunable Dodecagonal RIS Unit Cell for Disaster Recovery via MADNI Drone at Sub-6 GHz

This paper presents the design and simulation of a unit cell for a Reconfigurable Intelligent Surface (RIS) optimized to operate at 5.4 GHz, tailored for disaster recovery and search-and-rescue missions utilizing drones such as the Maneuverable Autonomous Drone for Navigation and Intelligence (MADNI). The RIS is intended to be deployed on MADNI drones to reestablish communication in areas where terrestrial infrastructure has been compromised. The unit cell features a dodecagonal geometry with a cross-shaped patch fabricated on a Taconic TLY-5 substrate, employing a 0.035 mm copper layer for both the top design layer and ground, interconnected via vias. Tuning capabilities are achieved by integrating a varactor diode with a capacitance range of 0.025 to 0.275 pF. Simulations conducted using CST Studio Suite demonstrate angular stability for both Transverse electric (TE) and Transverse magnetic (TM) modes up to 70° incidence. The TE mode exhibits a maximum 3 dB reflection loss with a center frequency deviation of 0.74%, while the TM mode shows superior stability with a maximum 1 dB reflection loss and a center frequency deviation of 0.18%. Additionally, the paper explores phase shift variations under different bias voltages, providing insights into the dynamic control of the RIS. These findings indicate that the proposed design offers a robust, tunable, and angularly stable solution for enhancing communication networks in disaster-stricken regions, particularly when integrated with advanced drone platforms like Maneuverable Autonomous Drone for Navigation and Intelligence (MADNI), which features 5G connectivity, obstacle avoidance, object detection, facial recognition, and real-time video streaming capabilities.